A process for installing the payload onto a subsea structure has the steps of affixing an adapter spool on to the subsea structure, deploying a plurality of winches in spaced relation to the subsea structure, connecting an end of a plurality of slings received on the plurality of sheaves to a plurality of winches, connecting an opposite end of the plurality of slings to the payload, lowering the payload in a direction toward the subsea structure, actuating the plurality of winches so as to draw the payload downwardly into a position on the subsea structure, and locking the payload onto the subsea structure. The adapter spool has a collar with a plurality of sheaves extending outwardly therefrom. The payload can be a capping stack and the subsea structure can be a blowout preventer.